Method for producing iron cement in powder form



Patented Mar. 24, 1953 METHOD FORPRODUCING IRON IN POWDER FORM Victor Trief, 'Deux-Acren Lez Less'ines, Belgium No Drawing. Application August 30, 1949, Serial No. 113,249. In Belgium September 3, 1948 2 Claims. 1 It is known to grind blast-furnace slag, after it has been previously-dried,- in order to obtain a commercial hydraulic binder in powder form, the catalyser thereof being added during or after the grinding. The catalyser generally used is Port- 5 land cement in clinker or in powder form, according to whether it is being added during or after the grinding of the slag.

It is also known to grind by a wet method granulated blast-furnace slag in order to obtain, under the form of a paste, a hydraulic binder of very fine grainsiae, and one that has latent hydraulicbinding properties, which thus appear only after the binder will be put in the presence of a catalyser such as Portland cement for example.

Such grinding by the 'wet method is known to show very greatadvant'age's over the dry grinding,

' since. it enables to obtain a fineness of the ground particles as is impossible to achieve by the dry grinding into powder. Moreover, it enables a large saving in the required motive power. Finally, it obviates the serious drawbacks encountered with the simultaneous dry grinding of the slag and its catalyser, which dry grinding yields respective grain sizes of the slag and its catalyser, which are insufficient and in reverse relationship with respect to what is necessary in order to obpracticallybe prepared on the spot of use and,

moreover, must virtually be used as its production proceeds, considering the need of agitation.

Preparing the paste in situ and keeping it constantly in movement requires the mounting of a suitable grinding and triturating plant. on the yard. It has been found that the binder would lose its qualities if it is stocked in the state of a paste without permanent precautions as to tem perature and agitation; consequently, a very important progress is achieved if the slag which has been ground by the wet method may, after grinding, be brought into a state that will enable it to be stored, with all the qualities inherent to the said paste, and under the form mostly convenient for'its stockage and for its subsequent use at any time with the proportion of catalyser correspond ing to. the quality of the types of concrete to be produced.

' is not added unless at the moment of use.

The present invention brings into efiect the possibility of storing, under a suitable form, the above specified hydraulic binder and enables to convert the paste obtained by wet grinding, into a powder that-retains all the initial qualities of the paste, it is to say that the original paste may be reconstituted by simply mixing the powder with water. i

To this end, and according to the invention, the binder in powder form is obtained by drying the paste resulting .from the wet grinding of the granulated slag, immediately after grinding, such drying being preferably carried out at a relatively low temperature, as rapidly as possible, in thin, segregating layers.

To this end the water is in the first place partially removed from the paste. This step may be carried out without the action of calorific energy and without direct man-power, in any suitable apparatus such a for decanting, filterin'g'or centrifugal drying, or with the help of any other means enabling tc'remove a large proportion of the water contained in the paste. The thus treated material is subsequently advantageously subjected to a drying action, which may, if desired, be completed by a dispersing action in suitable apparatus which eliminates the remainder of the water; thermal energy, vacuum, infra-red rays, radio-frequency, or any other agent may be used to this end. Such apparatus may be constituted e. g. by rotary bullet or blade dryer. At the end of the latter step the treated product appears under the form of an extremely fine powder having completely dispersed particles.

It should be noted that the steps of dehydration and dispersion above described are conveniently carried out in such conditions that the temperature of the mass remains relatively low, advantageously lower than 50 C., so as to eliminate any danger of altering the treated product. Putting the particles into a state of complete dispersion results in securing such a pulverization that the grain size obtained is still smaller than that of the initial paste.

It will be understood that owing to the fact that the paste is thus transformed into a powder retaining all the hydraulic properties of the slag, it becomes possible to use such hydraulic binder, with all its advantages, in any place, at any time and without limitation of stocking time.

The said powder maybe supplied in sacks, undergo transportation or be kept in a store, without the risk of alteration, provided the catalyser Contrary to this, conventional cements containing the catalyser are very vulnerable to storage and transport and get the quicker "blown away and altered the greater the fineness to which they have been ground.

One of the essential features of the new process consists, moreover, in obtaining a powder of much greater fineness than can be achieved with the conventional dry grinding methods. The great fineness of particles obviates the well known drawbacks due to the fact that less finely ground iron cements do not retain water. Moreover, the speedof hydration of a hydraulic binder and, therefore, its hydraulic efiiciency, is a direct function of the fineness of its particles.

Finally, it is worth to mention the considerable economic advantage that results from the possibility of preparing and treating the above described binder in a central factory,'where it can be stored, and whence it can be despatched in sacks to the place of use.

Since the production of cement according to the invention does not require any burning of the mass, it may be effected in very simple installations, this being a great economical advantage. The powder cement according to the invention is also very advantageous for the preparation of very dry concrete, the use of which becomes more and more frequent. Indeed, if use is made of the paste obtained by wet grinding slag, which paste still contains a rather great proportion of water, it is necessary to add a relatively great quantity of Portland cement in order to obtain the desired water/cement ratio. On the contrary, when use is made of the cement according to the invention, such a convenient ratio may even be obtained without the addition of Portland cement, by simply using any catalyser, for instance a soluble base, such as soda, it being sufiicient to conveniently de- 'termine the quantity of mixing water.

I claim:

1. The method for the preparation of a hydraulic cement consisting of the steps of grinding blast furnace slag while wet to finely divided form, rapidly drying the ground product substantially immediately after grinding at a temperature below about C. to reduce the slag powder to dryness whereby the slag powder is capable of storage indefinitely without substantial loss of reactivity for cement formation, and mixing the powder with water and catalyst immediately in advance of use as a hydraulic cement.

2. The method for the preparation of a hydraulic cement consisting of the steps of grinding blast furnace slag while wet to finely divided form, removing the major portion of the water from the wet ground slag by mechanical means, rapidly drying the remainder at a temperature below about 50 C. to reduce the slag powder to dryness whereby the slag powder is capable of storage indefinitely without substantial 'loss of reactivity for cement formation, and mixing the powder with water and catalyst immediately in advance of use as a hydraulic cement.

VICTOR TRIEF.

REFERENCES CITED The following references are of record in the Great Britain 1931 

1. THE METHOD FOR THE PREPARATION OF A HYDRAULIC CEMENT CONSISTING OF THE STEPS OF GRINDING BLAST FURNACE SLAG WHILE WET TO FINELY DIVIDED FORM, RAPIDLY DRYING THE GROUND PRODUCT SUBSTANTIALLY IMMEDIATELY AFTER GRINDING AT A TEMPERATURE BELOW ABOUT 50* C. TO REDUCE THE SLAG POWDER TO DRYNESS WHEREBY THE SLAG POWDER IS CAPABLE OF STORAGE INDEFINITELY WITHOUT SUBSTANTIAL LOSS OF REACTIVITY FOR CEMENT FORMATION, AND MIXING THE POWDER WITH WATER AND CATALYST IMMEDIATELY IN ADVANCE OF USE AS A HYDRAULIC CEMENT. 